184 Report 8. A. A. Advancemknt of Science. 



(2) The smaller the diameter of a globule the larger its surface 

 comparatively. The total surface of all particles in a colloidal system 

 must of course be enormous. For instance, 1 c.c. of a substance as cubus 

 has a surface of 6 cm.- ]f it is split up into very small cubes of 0-1^ 

 length, the total surface is 60,000 m.- 



(3) Hence it is evident that in colloidal systems surface energies, 

 absorptions and superficial condensations play a dominant role. 



(4) The (either positive or negative) electrical character of the 

 colloid globules stipulates the possibility of their being influenceil by 

 electrical energy. 



If two colloids of different electrical charges are mixed in a certain 

 proportion a precipitation takes place. The positive and negative par- 

 ticles absorb each other, forming neutral complexes and deposit. The 

 optimal concentrations not having been observed, no precipitation 

 occurs and both colloids can exist beside each other. It is even 

 possible to dissolve the precipitate again by adding one of the com- 

 ponents in excessive quantity ; the resulting mixture has the electrical 

 character of this latter component, but with regard to other peculiari- 

 ties is somewhat different. Also colloids which have the same elec- 

 trical charge are not indifferent in mixtures towards each other. Some 

 of them added in xevy small (juantities to another give it a very great 

 resistance against electrolytic or thermal influences. Or adversely, it 

 is possible to make, for instance, a negative colloid very sensitive by 

 the addition of another negative one. 



It has to be expected that in mixtures of electrically different, or 

 in those containing colloids of the same electrical chai-acter, the velocity 

 of the convective transport is other than that in one of the pure 

 components. 



This has to be admitted also in colloids to which electrolytes are 

 added. The more precipitating ions — kations for negative and anions 

 for positive colloid solutions — are added, the less vivacious is Brown's 

 molecular movement and the velocity <>f the electrical transport 

 (Freundlich). As soon as the colloid is neutralised it precipitates and 

 takes the precipitating ion absorbed with it. Generally the precipi- 

 tating power is stronger the higher the valency of the active ion. 



The other ion, with the same electrical character as the colloid, 

 is not inactive during the process of piecipitation ; it exercises an 

 antagonistic or disseminating infiuence according to its nature. 



It is evident that for the precipitation the absorbing forces of the 

 extensive surfaces in the colloid are of great importance, and it has 

 been proved for some special cases that the degree of absol-ption of 

 an ion is proportional to its precipitating or disseminating power 

 (Freundlich). 



{/)) The Blood. 



All that has beeji said of colloids in general holds good for the 

 colloids of the organism. These latter ai-e not all simple, but in com- 

 plexes and in combination and co-relation with electrolytes. An 



